Altimeter



Nbv. s, 1938. c. H. H; RODAVNETQ ALTIMETER 4 Sheets-Sheet 2 Filed April 24, 1936 I INVENTOR CHARLES H ILA! RE HENRI RODANE/T M0QZAZ ATTORNEYS Nov. 8, 1938. c. H. H. RODANET ALTIMETER' 4 Sheets-Sheet 3 Filed April 24, 1936 Fie'f IINVENTORI CHARLEG HILAIRE HENRI RODANET BV gb ATTORNEYS Nov. 8, 1938. c. H. H. RODANET 2,135,950

ALTIMETER Filed April 24, 1956 4 Sheets-Sheet 4 Fieb.

INVENTORI C CHARM-I6 HILAIREHENR! RODANET ATf'ORNEYS Patented Nov. 8, .1938

UNITED STATES 2,135,950 surnun'rnn Gharles Hilaire Henri Rodanet, Neuilly-sur- Seine, France, assignor to Socit Anonyme: Etablissements Ed. Jaeger, Levallois-Perret, France Application April '24, 1936, Serial No. 76,193 In France May 8, 1935 1 Claim.

This invention relates to altimeters. The main object of the invention is to advantageously utilize hard stones as bearings for the various pivot pins of the movable members of 5.. the altimeter.

This arrangement has been found, in practice, to be absolutely indispensable for the construction of an apparatus, the index of which moves in a regular and smooth manner. In fact, the i friction coefll'cient changes considerably from the state of rest to the state of movement. Consequently,the resilient diaphragm has heretofore been subjected to a resilient distortion before it could actuate the index, owing to the friction 135.. present, which, although very slight, cannot be considered as negligible with a geared up ratio.

Then, when the movement had begun, the value of the friction diminished and the diaphragm could relax as a spring. The index therefore 20 moved' in jerks. y.

Y Another object of the invention provides an altimeter wherein compensation of the temperature during. functioning thereof is automatically eflected.

25 Generally speaking, the altimeter according to .the invention allows:

(1:) Of reducing 'to the minimum prejudicious resistances, I

(b) Of improving the accuracy of the reading, 30 (0) Of obtaining an automatic compensation in function of the variations of the temperature, id) Of adiusting'the amplification ratio, 7 (e') Of adjusting the position of the indicating means, I 1 3.5, (f) Of adjusting the position of the'barom'etric scale. The invention furthermore relates to other particular features which will appear in the followingdescription with reference to the accom- '40 -.panying drawings given by way of example only and in which:

' Fig. 1 is an'axial section made according to line 1-1 of Fig. 2, of an improved altimeter according to the invention.

Fig. 2 is a front view thereof.

Fig. 3 is a section made according toline III-- III of Fig.2 showing the device for adjusting the position of the vacuum box.

Fig. 4 is an underside plan view of the appara- ;tus, the casing and various mechanisms being removed.

Fig. 5 is a detail view, on an enlarged scale of the amplifying device. Fig. 6 is a section made according to line VI-- 5 VI of Fig. 5 and shows, on an enlarged scale, the

ble diaphragm of said vacuum box. According to the invention, this wall I has a relatively great thickness, so that whatever maybe its distortions, due to the variations of pressure exerted on said wall and obviously included within the limits of utilization of the altimeter, they are always inferior to the limit of the resiliency; consequently, no permanent distortion of said (1111- phragm is produced. Moreover, this important thickness prevents the rapid deterioration of said diaphragm under the action of atmospheric agents, as occurs when use is made of very thin diaphragms, in view of obtaining high responsiveness of the apparatus. V

The rigid bottom I of said vacuum box com prises a boss 3 or the like forming a part of said bottom or secured on the same in afluid-tight manner. In this boss 3 is formed an internally threaded blind hole 4 in which fits a screw I serving to rigidly hold a resilient blade 6. This resilient blade 8 bears at both its ends on the lower part and in two recesses formed in two rigid pillars I and- 8 secured at theirv ends by any as suitable means and, for instance, by riveting to the two plates 9 and iii of the apparatus (Fig. 4)

' The distortion of the blade 0 is such that it tends to press the bottom I of the vacuum box against the upper part of the pillars I and 8. 0

As indicated above, the bottom I rests only on one of the pillars; for instance the pillar 1 and it is guided and held in position by a projection i I which enters a corresponding radial perforation I2 formed in said pillar 1. On the opposite side,

the bottom I comprises a projection II which enters a radial perforation ll formed in pillar 8 (Fig. 3). This pillar 8 has an axial bore I! internally threaded at l6 and in which enters a corresponding screw This screw ll terminates in a conical portion 18, itself terminating in a guide and stop cylinder Ill. The projection I3 is pressed,

' under the action'of the resilient blade 6, against the conical portion i8 and it will be seen that, by suitably rotating the screw l1 determining an y axial displacement of the conical portion l8, the level of the bottom I of the vacuum box can be adjusted relatively to pillar 8.

On the distortable wall 2 of the vacuum box is secured, by any suitable means and, for instance, by welding, a lug, projection or the like on the upper part of which is secured, by means of a ,screw 2| for instance, a bimetallic blade 22. The free end of the latter is slotted to form a fork member and receives a shaft 23 or the like, on which is journalled a link 24. The other end of this link is pivotally mounted on a shaft 25 which is secured in the arm 26 of a bell-crank lever pivoted on a fixed stud 2'1. This stud 21 is pivoted by means of hard stones on two plates 28 and 29 rigid together, the plate 29 being itself rendered rigid with the rear plate 10 by means of two rigid pillars 38 and 3|. The plates 28 and 29 are connected by pillars 32 and 33 whilst the plates 9 and ID are connected by the three pillars l, 8 and 16.

The free end of the second arm 34 of the bellcrank lever is connected, by a stud 35, to a link 36 the other end of which is pivoted, by means of a stud 31,to a fork member 38. According to the invention, the various pivotal connections of the amplifying device which has just been described are particularly carefully machined for avoiding any play. For that purpose and as shown in Fig. 6 of the drawings, which illustrates in greater detail and in section, one of the pivotal connections and that, for instance, between the arm 34 of the double bell-crank lever and the link 36, the stud 35 is secured to the arm 34 in any suitable man ner, so as to avoid any play. In a suitable perforation of the link 36 is set, in the known manner, a hard stone 39 having a central perforation in which fits, without play, the stud 35 of the pivotal connection. The other pivotal connections are constituted in a similar manner.

As indicated above and according to the invention, in view of compensating the variations of distortion of the diaphragm 2 of the vacuum box for one and the same pressure when the temperature varies, the link 36 can be constituted (see Fig. 7 by a curved bimetallic blade suitably chosen so that its distortion in function of the temperature modifies the amplification ratio to an extent corresponding to the variation of distortion of the diaphragm 2 for this temperature, but with a reverse sign to said variation. In any case, hard stone or jewel bearings 39, 39 may be inserted in portions of the link to remove friction. The fork member 38 is rigid with the end of a resilient blade 42 the other end of which is secured, by a screw 40, for instance, .to the end of a rigid lever 4|. This lever 4| is fast on a shaft 43 which is mounted, by means of two counterpivots, on the plate 28, on the one hand, and on the front plate 9, on the other hand. Near the end of shaft 43 located adjacent plate 9 is secured a gear sector 44 suitably balanced and toothed at its periphery for meshing with a pinion 45 fast on a stud 46 one of the ends of which, located in front of plate 9, carries the index 41.

The blade 42 resiliently bears, at its free end, on a screw 48 screwed in a corresponding inter nally threaded portion of lever 4|. It will be seen that byscrewing or unscrewing the screw adjustment of the amplification ratio of the device, is obtained.

The stud 46 on which are rigidly mounted the toothed pinion 45 and the index 41, is mounted on the front plate 9 by means of a hard stone 4! and on a plate 58 by means of a counter-pivot made of stone of the type of those used in clocks making. The plate 50 is connected to the front plate 9 by two rigid pillars 5| and 52. A spiral spring 53 restoring the index 41 to zero, has one of its ends connected to the stud 46 whilst its other end is secured to a pillar 54 mounted on the front'plate 9.

The amplification ratio of the device described above is suitably determined by a judicious choice of the ratio of the arms 26 and 34 of the bell crank lever, of the distance between the stud 31 and shaft 43 and of the ratio of the gear sector and pinion 45.

On the front face of the plate 9 is secured, by means of screws 55, a dial 56 comprising a graduation corresponding to the usual barometric pressures at the ground, for instance, in millimeters of mercury.

The plate 9 comprises, on its front face, a circular recess 51 concentric with the stud 46 of the index 41 and in which fits a disc 58. This disc 58 is relatively resilient so as to frictionally engage, on the one hand, with the rear face of the dial 56 and, on the other hand, with a peripheral circular projection 59 of plate 9. The disc 58 is toothed at its periphery and meshes with a pinion 60 provided on a pin 6| journalled in the casing 62 of the apparatus, the end of the pin 6| situated outside the casing 62 being provided with a milled knob 63 facilitating the rotation of said pin 6!. The disc 58 carries suitable "graduations opposite which moves the index 41 and which indicated preferably the altitudes directly in meters.

The casing 62, perfectly fluid-tight and preferably made in one piece, is secured, by means of three screws 64 for instance, on the rear plate ill of the apparatus. The plate 9 preferably frictionally fits into said casing 62 the front face of Which is obturated by a glass plate 65. This glass plate 65 of circular shape, fits into a suitable recess of the casing and bears against the edge of said recess preferably with interposition of a raised part 66. l

The glass plate '65 is held in position by means of a rim 61 or the like secured on the casing 62 by means of screws or screw-threadedsockets 63, or the like. In order to ensure perfect fluidtightness, between the flange of the rim 61 and the glass plate 65 is interposed a ring 68 made of rubber or like material.

The interior of the fluid-tight casing thus constituted is placed in communication with the atmosphere by a suitable piping (not shown). It is in fact indispensable that the interior of the apparatus should be in direct communication with the atmosphere. In fact, the altimeter is usually located in the pilot's cockpit or in the cabin and this place is not usually at the same pressure as the exterior. For that purpose, the casing 62 comprises, at its rear part, a tubular connection 89 or the like on which fits the pipe communicating with the atmosphere.

According to the invention, the tubular connection 69 is arranged co-axially with the screw I! (Fig. 3), so that for adjusting this screw, it suffices to remove the piping. Once the apparatus is adjusted, any risk of commimication between the interior of the casing 62 and the at- Yposlte the point of the mosphere, otherwise than through the tubular connection 89, is avoided.

The operation of the altimeter according necessitate complementary explanations. Concerning the various adjustments, the latter are eiiected in the following manner.

(a) Adjustment of the amplification ratio.- This adjustment, effected once for all, except concerning the thermostatic adjustment which, it provided, takes place automatically, is obtained by acting on the screw 48.

- (b) Adjustment of the position of the altimetric. graduation-It will be assumed that this adjustment takes place at a. point situated atsea level, that is to say at zero of the altimetrlc scale, the operator then turns the dial 58 bearing said'scale by means of the milled knob so as to'move the zero of the graduation. opposite a point of the graduation of the barometric scale of disc 56 corresponding to atmospheric pressure at the instant and at the place considered.'

If the adjustment is effected at an altitude different from zero, the graduation of the alti'metric scale correspondingto this altitude is moved op- I graduation of the barometric scale corresponding to atmospheric pressure at the instant and at the place considered.

(e) Adjustment of the 0 position of the indea:.- -It will takes place at a-point situated at sea level, that 5 power transmission lever happens to be.

is to say at zero of the altimetric scale, the oper-y ator then acts on the screw l1 until the index 41 is moved opposite the 0 of the scale.

It the adjustment is eiiected at an altitude ditierent from zero, the index 41 is moved opposite the point of the graduation of the altimetric scale corresponding to the altitude where one In the diagrammatic embodiment illustrated in Fig. 8, a device is shown allowing to eflect two corrections: one ensuring the flxity o! the zero,

interposed between the to the invention will be easily understood and does notbe assumed that this adjustment andthe other correcting the length of the diaphragm of.the vacuum box and the movable unit controlling the indicating means.

In the example of Fig. 8, the bimetallic blade 2" is rigidly secured, at 23i, on a right-angled lever at 221, pivotally mounted at 2|8. The other end of the blade 2" is pivoted, at 25", to a link 24" pivotally connected at 23 to a diaphragm 2112 of a vacuum box 2". The bimetallic blade 2" is sodevised that, under the action of the temperature and for a constant pressure, it corrects the collapsing of the diaphragm. The end 25" reaches particularly 25k whilst the pivotal connection 23" reaches23k, the distances 25"-25k and 23"-23k being equal.

The bimetallic blade H1 is rigidly secured at one end, at 232, to the lever 221 and it is pivotally mounted at its other end, at 233, to the members transmitting the movement to the index 4110. This bimetallic blade 2i1 corrects the length 1| oi lever 221 for compensating the too important distortability or rigidity of the diaphragm 2m of the vacuum box 2" when the pressure varies (altitude).

What I claim as my invention and desire to secure by Letters Patent is: l In an altimeter oi the type having at least one vacuum box, the combination with a casing, of i ndicating members, an ,operative mechanism interposed betweensaid vacuum box and said indicating members and comprising a motion transmitting lever, a first bimetallic blade rigidly se-' cured at one end to said lever and at its other end having a rod by which it is articulated to said vacuum box so that said other end of the blade will follow the displacements of said vacuum box as a iunctionor'the temperature at constant pressure, and a second bimetallic blade rigidlysecured at one end to said motion transmitting lever and at the other end being articulated to said operative mechanism Ior transmitting motion to the indicating members, said second bimetallic blade being capable of altering the eiiective length of said motiontransmitting lever as a function of the temperature. CHARLES mAIR-E HENRI RODANE'I. 

